diff --git a/.gitignore b/.gitignore
index 196e176..bca3248 100644
--- a/.gitignore
+++ b/.gitignore
@@ -17,3 +17,9 @@ Cargo.lock
 # Added by cargo
 
 /target
+
+## IntelliJ IDEA ###
+.idea
+*.iws
+*.iml
+*.ipr
\ No newline at end of file
diff --git a/Cargo.toml b/Cargo.toml
index 84a0adb..aca5246 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -6,3 +6,5 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+sha1 = "0.10.6"
+hex = "0.4.3"
\ No newline at end of file
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..dde4911
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,3 @@
+// 不使用lib.rs的话，就无法在tests里引用到src中的模块
+pub mod objects;
+pub mod utils;
\ No newline at end of file
diff --git a/src/main.rs b/src/main.rs
index e7a11a9..89e2949 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,5 @@
+use std::collections::HashMap;
+type Index = HashMap<String, bool>;
 fn main() {
     println!("Hello, world!");
 }
diff --git a/src/objects/blob.rs b/src/objects/blob.rs
new file mode 100644
index 0000000..ed3dcaa
--- /dev/null
+++ b/src/objects/blob.rs
@@ -0,0 +1,6 @@
+use crate::objects::object::Hash;
+#[derive(Debug, Clone)]
+pub struct Blob {
+    hash: Hash,
+    data: String,
+}
\ No newline at end of file
diff --git a/src/objects/commit.rs b/src/objects/commit.rs
new file mode 100644
index 0000000..e69de29
diff --git a/src/objects/mod.rs b/src/objects/mod.rs
new file mode 100644
index 0000000..e0c18af
--- /dev/null
+++ b/src/objects/mod.rs
@@ -0,0 +1,4 @@
+pub mod commit;
+pub mod blob;
+pub mod tree;
+mod object;
\ No newline at end of file
diff --git a/src/objects/object.rs b/src/objects/object.rs
new file mode 100644
index 0000000..ff70033
--- /dev/null
+++ b/src/objects/object.rs
@@ -0,0 +1 @@
+pub type Hash = String;
\ No newline at end of file
diff --git a/src/objects/tree.rs b/src/objects/tree.rs
new file mode 100644
index 0000000..e69de29
diff --git a/src/utils/mod.rs b/src/utils/mod.rs
new file mode 100644
index 0000000..929d03a
--- /dev/null
+++ b/src/utils/mod.rs
@@ -0,0 +1 @@
+pub mod util;
\ No newline at end of file
diff --git a/src/utils/util.rs b/src/utils/util.rs
new file mode 100644
index 0000000..c228431
--- /dev/null
+++ b/src/utils/util.rs
@@ -0,0 +1,11 @@
+use sha1::{
+    Digest,
+    Sha1
+};
+
+pub fn calc_hash(data: &String) -> String {
+    let mut hasher = Sha1::new();
+    hasher.update(data);
+    let hash = hasher.finalize();
+    hex::encode(hash)
+}
\ No newline at end of file
diff --git a/tests/test.rs b/tests/test.rs
new file mode 100644
index 0000000..e240b16
--- /dev/null
+++ b/tests/test.rs
@@ -0,0 +1,42 @@
+use sha1::{Sha1, Digest};
+use std::fs::File;
+use std::io::{Write, BufReader, BufRead, Error};
+
+#[test]
+fn test_hash() {
+    let mut hasher = Sha1::new();
+    hasher.update(String::from("hello world"));
+    let result = format!("{:x}", hasher.finalize());
+    println!("{}", result);
+    println!("{}", mini_git::utils::util::calc_hash(&String::from("hello world")));
+}
+
+#[test]
+fn test_write() -> Result<(), Error> {
+    let path = "lines.txt";
+    //create会截断文件
+    let mut output = File::create(path)?; // ? 用于传播错误
+    write!(output, "Rust\nWrite\nRead4")?;
+    Ok(())
+}
+
+#[test]
+fn test_read() -> Result<(), Error> {
+    let path = "lines.txt";
+    let input = File::open(path)?;
+    let buffered = BufReader::new(input);
+
+    for line in buffered.lines() {
+        println!("{}", line?);
+    }
+    Ok(())
+}
+
+#[test]
+fn test_string() {
+    let mut s = String::from("Hello");
+    s.push_str(", world!");
+    s += "2";
+    s.push('!');
+    println!("{}", s);
+}
\ No newline at end of file